<form action="<?php echo url_for("@login"); ?>">
    <table style="margin: 0 auto; margin-top: 200px; border: 1px solid black; padding: 10px;">
        <tr>
            <td>Usuario</td>
            <td><input type="text" /></td>
        </tr>
        <tr>
            <td>Contraseña</td>
            <td><input type="password" /></td>
        </tr>
        <tr>
            <td colspan="2" align="center">
                <input type="submit" value="Entrar" />
            </td>
        </tr>
    </table>
</form>